The starting point for this is the bubble level according to the CH-PS 463 803, where the metal section in one case has a cylindrical seat, and in the other case a conical seat for directly receiving the corresponding cylindrical or conical level tube. Before the level is installed in its seat, the jacket surface of the level tube and the inside surface of the seat are smeared with an adhesive. More adhesive is applied to grooves which are disposed partly in the level tube and partly in the window of the hollow metal section. After the level tube has been inserted and adjusted, this adhesive is supposed to bond so as to guarantee a reliable seat. Premature bonding of the adhesive would impair the adjustment here. On the other hand, if the adhesive hardens too slowly, there is a risk of misadjustment in the meantime. The hardening of such adhesives is associated with an unavoidable volume change. This entails a further risk of causing a defective adjustment. Furthermore, the applicant expressly refers to the adhesive in such bubble levels tearing off as a consequence of temperature and/or humidity. From this it follows that the accuracy of such bubble levels is only limited.
Starting from this prior art, a different design of bubble level (Gm 83 34 916) strives for a high degree of measurement accuracy. Here, the section and the level tube have mutually aligned holes, grooves, or webs, which are supposed to fix the level tube in such a fashion that readjustment is obviated. However, practical experience has shown that such a solution is not achievable, since it leaves out of account the manufacturing tolerances of the utilized components. The various possibilities for installing horizontal levels in the hollow section of the bubble level, while perfectly adjusting the level tube in a seat that is situated in a window of the hollow section cannot be so easily transferred to vertical levels, however. The problem of achieving particularly high accuracy with relatively little expenditure, even for the vertical levels, consequently appears unsolved now as before.